1. Field of the Invention
This invention relates to a collision record apparatus, a collision state estimation method and a record medium for recording the state of a vehicle when a collision of the vehicle occurs.
2. Description of the Related Art
JP-A-5-270352 discloses a collision record apparatus. As shown in FIG. 4, a microcomputer 1 has an operation control section of an air bag and a diagnosis section. The operation control section makes a collision judgment based on a detection output from an acceleration sensor 6. The diagnosis section detects a failure of an acceleration switch 2, a squib 3, etc., by turning on and off a transistor 4 for an extremely short time. The diagnosis section measures the elapsed time since occurrence of the failure (or equivalent state) and then writes the failure contents and the elapsed time since occurrence of the failure into nonvolatile memory 5.
The microcomputer 1 detects the maximum value of the acceleration sensed by the acceleration sensor 6 as a magnitude of a collision. The microcomputer 1 measures the elapsed time since the acceleration reached the maximum (timer value) and then writes the maximum acceleration and the elapsed time into the nonvolatile memory 5 (see FIG. 5).
Consequently, after the collision, the relative time relationship between the failure occurrence and the collision occurrence can be estimated precisely based on the record contents read from the nonvolatile memory 5 (see FIG. 5), namely, the elapsed time. At the same time, the failure contents and the collision degree can also be grasped, making it easy to track down the relationship between the operation state of the air bag and the failure of the operation control section of the air bag.
The collision record apparatus writes the maximum acceleration and the elapsed time into the nonvolatile memory 5 and after the collision, keeps track of the collision state based on the maximum acceleration and the elapsed times in the nonvolatile memory 5. However, upon occurrence of a vehicle collision, it is difficult to make an assumption about the details of the vehicle collision based on a record of one data of the maximum acceleration and the elapsed time, since the waveform of the acceleration drastically varies. In general, this kind of apparatus provides less data indicating the state in which the vehicle collides and is broken, and it is not necessarily easy to track down the cause of the accident.
On the other hand, to solve the problem, it is also considered that acceleration data actually occurring at the collision time is not processed and is stored in memory as waveform data. However, to put the idea to use, for example, memory of a large capacity of at least about several mega bytes becomes necessary, leading to a drastic increase in cost and the idea is not practical; this is a problem.
It is therefore an object of the invention to record data indicating the feature point when a vehicle collides and is broken, and to make it easy to track down the cause of the collision with a small memory capacity.
According to the invention, there is provided a collision record apparatus for recording times at which a collision waveform provided accompanying a collision of a mobile unit and a waveform derived from the collision waveform reach their respective setup threshold values and waveform types in memory in association with each other.
In the collision record apparatus according to the invention, the time is the elapsed time from the time at which the collision waveform exceeded a predetermined reference value to the time at which the waveform reached the setup threshold value.
According to the invention, there is provided a record medium recording the times at which a collision waveform provided accompanying a collision of a mobile unit and a waveform derived from the collision waveform reach predetermined values in memory in association with waveform types.
According to the invention, there is provided a collision estimation method comprising the steps of starting time counting based on the timing at which a collision waveform provided accompanying a collision exceeds a predetermined reference value, calculating the time when a waveform derived from the collision waveform exceeds a predetermined threshold value set for the waveform based on the counted time, recording the calculated time in a record medium in association with the waveform type, then reading the time recorded on the record medium for each waveform type as required, comparing the read contents with provided experimental measurement data, and estimating a situation when the collision occurred.